It may be desirable to accurately determine exhaust temperatures of an engine. By determining engine exhaust temperatures, it may be possible to provide mitigating actions when exhaust temperatures may be higher than is desired. Further, determining exhaust temperatures may be useful for assessing operation of exhaust after treatment devices. One way to determine exhaust temperatures is to install thermocouples, thermistors, or other temperature sensors in an exhaust passage that directs engine combustion by-products to exhaust after treatment devices. However, the thermocouples or thermistors may degrade if they are exposed to higher exhaust temperatures. Further, performance of exhaust temperature sensors may degrade if acidic combustion byproducts accumulate on the temperature sensors. Therefore, it may be desirable to determine engine exhaust temperatures in a way that reduces the possibility of sensor degradation. Further, it may be desirable to determine exhaust temperatures in a way that is accurate and dynamic such that rapid changes in exhaust temperatures may be observable.
The inventors herein have recognized the above-mentioned disadvantages and have developed a method for an engine, comprising: estimating an offset for a resistance value of an exhaust gas sensor heater element relative to an engine operating temperature; and estimating an engine exhaust gas temperature based on the resistance value of the exhaust gas sensor and the offset.
By estimating exhaust temperature via a heater of an oxygen sensor, it may be possible to provide the technical result of measuring exhaust temperature via a sensor that is protected from exhaust system conditions. For example, an oxygen sensor heater element may be protected via a metallic shroud that covers the oxygen sensor and its heating element. Further, by determining an offset value for the oxygen sensor resistive heating element, accuracy of exhaust temperature measurements may be improved. Consequently, it may be possible to provide accurate exhaust temperatures via a sensor that has at least some protection from conditions within an engine exhaust system.
The present description may provide several advantages. Specifically, the approach may improve exhaust gas temperature estimates. Additionally, the approach may reduce exhaust gas temperature sensor degradation. Further, the approach may compensate for exhaust temperature sensor changes that occur over time, instead of one time sensor compensation.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.